This application is based upon and claims priority of Japanese Patent Application No. 2000-3837, filed, the contents being incorporated herein by reference.
The present invention relates to a semiconductor device and a method for fabricating the semiconductor device, more specifically to a semiconductor device comprising the capacitors formed of ferroelectric film.
An FRAM (Ferro-electric Random Access Memory) is a nonvolatile semiconductor memory using ferroelectric film as dielectrics of the capacitors. The FRAM is much noted for the high operation speed and low electric power consumption.
A structure of the capacitors of such FRAM will be explained with reference to FIG. 12. FIG. 12 is a conceptual view of the capacitors of the conventional semiconductor device.
As shown in FIG. 12, an IrO2 film 130 and a Pt film 134 are formed the latter on the former, and the IrO2 film 130 and the Pt film 134 form a lower electrode 136.
A ferroelectric film 138 of a PbZrxTi1xe2x88x92xO3 (PZT) film or a SrBi2Ta2O9 (SBT) film is formed on the lower electrode 136.
An IrO2 film 140 and a Pt film 144 are sequentially formed on the ferroelectric film 138. The IrO2 film 140 and the Pt film 144 form an upper electrode 146.
The lower electrode 136, the ferroelectric film 138 and the upper electrode 146 form a capacitor 148.
However, in a case that, as shown in FIG. 12, the lower electrode 136 and the upper electrode 146 of the capacitor 148 are formed of Ir-family films, it is difficult to realize low-voltage operation and hydrogen deterioration resistance, which are required by the next generation devices.
As an electrode material which is able to realize improved low-voltage operation and hydrogen deterioration resistance, SRO (SrRuOx) film is noted. SRO film, which has perovskite structure, as have PZT and SBT, is not easily damaged in semiconductor device fabrication processes, and is expected to realize low-voltage operation. SRO film is a material of high resistance to hydrogen.
However, a capacitor formed of SRO film used as an electrode material Pb or Bi contained in the ferroelectric film tend to diffuse into the SRO film.
In view of this, a technique which can realize low-voltage operation and hydrogen deterioration resistance by using SRO film.
An object of the present invention is to provide a semiconductor device which can realize low-voltage operation and hydrogen deterioration resistance by using SRO film.
The above-described object is achieved by a semiconductor device comprising: a first electrode; a ferroelectric film formed on the first electrode; and a second electrode formed on the ferroelectric film, the first electrode or the second electrode comprising SrRuOx film with Pb and/or Bi added. Pb and Bi are added to the SRO film, whereby the diffusion of the Pb and Bi contained in the ferroelectric film into the SRO film are suppressed, which leads to an improvement of the capacitor ferroelectric properties. Thus, the semiconductor device can realize low-voltage operation and hydrogen deterioration resistance by using the SRO film.